bang their ***.
Go into a locker room (or anywhere for that matter) and jam a toothpick deep into the locks of all the locked lockers. Sweaty bastards won't be able to change clothes, lol.
That's a shitty thing to do. If you have more time before the mark comes back use toothpaste instead. That **** dries as hard as concrete and you can't use tweezers to get the **** out.